New Technology May Prolong the Life of Devices

"One of the biggest problems with any kind of implanted device, such as pacemaker, a chemotherapy port or the glucose sensors necessary to monitor blood sugar levels in diabetic patients, is the body's natural reaction to recognize it as foreign and form a scar around it," said Doctor Stuart Williams, a senior investigator on the study. "Scars have very little blood flow and because this connection between the body and the device is compromised, the function of the device over time can decline, threatening health and leading to additional interventions to replace it."

The researchers sought to prevent the formation of scar tissue around an implanted device by "pre-vascularising" the device just prior to implantation. The investigators call this a microvascular construct (MVC) consisting of tiny blood vessel fragments suspended in a collagen gel. The combination of the MVC, already rich with blood vessels, and the device appears to provide an environment that resists the formation of scar tissue once the device is implanted, Williams said.

The researchers compared the tissue surrounding a bare expanded polytetrafluoroethylene material embedded in collagen alone to one embedded in collagen and the MVC, and found that the latter both promoted and maintained circulation in the area around the implant, Williams said. Animal models were used. Collagen is a naturally occurring protein found in the flesh and connective tissue of animals and humans. It has been found to mediate the inflammatory reaction that often occurs when an implanted device interacts with surrounding tissue.

"We found that the presence of the MVCs and collagen altered the way tissue formed around the implants, restricting the formation of scar tissue because there was so much blood vessel activity," Williams said. "The presence of the MVCs and collagen also reduced the number of white blood cells that stimulate inflammation, where the device was implanted. The vessels associated with the implant were seen to be capable of sustainable blood delivery over time." All of these factors are important in sustaining circulation and suppressing scar formation, he said.